Preliminary results have shown the presence of four minor cocaine-related alkaloids in most illicit cocaine samples; these are tropacocaine, norcocaine, and and the isomers cis-cinnamoylcocaine and trans-cinnamoylcocaine. The variations in the relative amounts of these alkaloids suggest that they might be useful for comparison purposes. Gas chromatography analysis of concentrated cocaine samples showed the reproducibility of the area ratios of tropacocaine, norcocaine, and cis- and trans-cinnamoylcocaine to cocaine within subsamples of large lots of illicit cocaine. These intrasample variations were much smaller than the variations among a random sample of cocaine exhibit materials submitted for routine analysis and quantitation. To draw meaningful conclusions regarding the similarity of two cocaine samples, data must also be available to show their dissimilarity to most of the unrelated cocaine samples. A large database of alkaloid/cocaine area ratios can quickly be searched by computer for any possible matches. The combination of four ratios for each cocaine sample greatly increases the selectivity of the comparison. Positive matches can then be further checked by visual comparison of chromatograms. 3 figures, 2 tables, and 21 references